Multiple Service Contracts and Indigo - Consuming external services with a generated proxy

Now you will implement the external client application and invoke service operations over HTTP. In this case, the client will rely on the WSDL document to generate a proxy and related configuration to call the service. This exercise will illustrate how the proxy generation process handles multiple contracts and endpoints.

1. Start by running theHostproject so that you can generate proxies for each service.
   
2. Go to theExternalClientproject in Solution Explorer and add a service reference forServiceA. Provide the base address http://localhost:8000 and name the referenceServiceA. This will generate a proxy for each contract exposed byServiceAand create an application configuration file with client endpoints.
   
3. Now add a service reference forServiceB. This time, provide the base address http://localhost:8001 and name the referenceServiceB. This will generate a proxy for each contract exposed byServiceB, adding new client endpoints to the application configuration file.
   
   The application configuration file is not overwritten when you add new service references. A merge is performed to add to configuration settings. SvcUtil also supports merge through command-line options.
   
4. This application will invoke each service using the proxies generated by SvcUtil. Like with theInternalClientapplication, you'll create a proxy reference for each service contract, initialize them in the form constructor, and then close them in theFormClosingevent. The code will be simplified somewhat since the generated proxy hides some of the complexity of creating the communication channel, and directly exposes close functionality. The resulting code is shown in Example 1-25.
   
   Example 1-25. Code to initialize and close generated proxies for ServiceA and ServiceB
   
   public partial class Form1 : Form
   {
     ServiceA.ServiceAClient m_proxyA;
     ServiceB.ServiceBClient m_proxyB; 
     public Form1()
     {
       InitializeComponent();
   
       m_proxyA = new ExternalClient.ServiceA.ServiceAClient("BasicHttpBinding_IServiceA");
       m_proxyB = new ExternalClient.ServiceB.ServiceBClient("BasicHttpBinding_IServiceB");
     }
     private void Form1_FormClosing(object sender, FormClosingEventArgs e)
     {
       this.m_proxyA.Close();
       this.m_proxyB.Close();
     }
   }
   
   You'll notice that each proxy is initialized by passing the name of a particular endpoint from the application configuration file. Each service exposes multiple endpoints, but because this is an Internet client, the assumption is that the
   client won't have permissions to call the TCP nor be able to invoke services over named pipes (named pipes requires same-machine calls). Still, add service reference generated configuration for all endpoints because the WSDL document includes all endpoints for a service.
   
5. Now you can add code to invoke each operation. If you look at the form in design view, you'll see that only three buttons are present to invoke the collective operations of both service contracts. Create Click event handlers for each button and add code to invoke each operation through the appropriate proxy. Example 1-26 shows the resulting code.
   
   Example 1-26. Code to invoke each service operation
   
   private void button1_Click(object sender, EventArgs e)
   {
     string s = m_proxyA.Operation1();
     MessageBox.Show(s);
   }
   private void button2_Click(object sender, EventArgs e)
   {
     string s = m_proxyA.Operation2();
     MessageBox.Show(s);
   }
   private void button3_Click(object sender, EventArgs e)
   {
     string s = m_proxyB.Operation3();
     MessageBox.Show(s);
   }
   
6. Compile and test the external client application. First run theHost, and then runExternalClient. Click each button to invoke the service operations exposed byServiceA andServiceB.

Let's look at the new concepts and tools introduced in this lab.

Please check back next week for the conclusion to this article.

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This article is excerpted from chapter 1 of the book Learning WCF A Hands-on Guide, written by Michele Leroux Bustamante (O'Reilly, 2007; ISBN: 0596101627). Check it out today at your favorite bookstore. Buy this book now.